As we’ve seen in my last post, sand is one of the commodities most in demand1. Here in the Netherlands, there is a whole industry built on the extraction and distribution of sand. One of the most used extraction methods is dredging, something we’re well acquainted with. One of the most used distribution methods is barge transport. And the National Dredging Museum has opened an exhibition on these complementary trades: ‘Sand on the Move’2.
Last Thursday was the opening of this new exhibition of the museum. For the occasion, there were two speakers invited. Kees van der Veeken, director Consortium Grensmaas showed us the current practice of sand mining. Tjeerd Roozendaal, head engineer – program director projects and maintenance of Rijkswaterstaat had the honour to open the exhibition. Afterwards, there was a dinner buffet available for the guests. An excellent opportunity to learn, hear opinions and build on your (dredging) network.
Our modern infrastructure was only made possible by the application use of sand as foundation of roads and fill material in concrete and tarmac. At the exhibition, there are displays of four big projects about sand mining: ‘Betuweroute’3, ‘Kraaijnbergse Plassen’4, ‘IJsseloog’5 and ‘Grensmaas’6. Each highlighting a certain aspect of sand mining in the Netherlands.
Another part of the exhibition revolves around the distribution of sand. And this posed a chicken and egg problem: in order to build roads, you need roads to transport the sand. So, in the early days, before there were roads, sand was being delivered over water by barge. There was a short period, where numerous small enterprises, mostly family owned, filled the gap of transporting sand by barge, taking the place of delivery trucks. Also my family had a motor vessel for sand transportation, ‘Excelsior’. And my grandfather told me many times of his adventures on board and his relative happy times. As this was hard work for sure.
Along with old photographs of those sand barges, there are also many models and a video exhibit. Each conveying respect to these men, women and sometimes children, that have been toiling to build the roads and railways that we are now taking for granted in our luxurious times.
Unfortunately, these businesses worked to their own demise. As roads and railways improved, there was less need to transport the sand by barge, but directly hauled to the location where it was needed by road. So, somewhere this typical business dried up. Nowadays, sand is still transported by barges, but they are usually owned by large companies, that own the whole product line from extraction, distribution to application.
There is also a small sand laboratory to experience yourself, how many different aspects of sand are involved in selecting the right sand for the right application. At a small scale and easy to understand steps, this represents how we are evaluating sand in our own laboratory. Next to this laboratory, there are many more kid friendly exhibits in the rest of the museum. I can highly recommend you to plan a visit to the national dredging museum these weekends or during the Christmas holiday.
We have another bright new MSc. engineer in dredging technology1: Gijs ter Meulen. Tuesday, he presented and defended his thesis on the forces and production of a trailing suction head. For this thesis project he was working at our research and development department at Damen Dredging Equipment2.
Trailing suction hopper dredges have become the tool of the trade for modern dredging contractors. They are versatile, flexible and able to transport sand over great distances. They load their cargo in their holds, by sucking up the sediment from the sea bottom with a big trailing suction head. This head looks like an out of size vacuum cleaner head.
Usually, it is very difficult to comprehend what is going on in and around the drag head. There is some laboratory research done, but not all results are freely available. Other knowledge is solely based on the experience of well-seasoned dredge masters. I do have respect for the experience of dredge masters, but their stories are hardly usable for an academic model description. So, Gijs took on the challenge to piece together a model, that satisfies our curiosity and fits with the experiences.
For this project, he identified several steps, which we briefly touch upon here:
The processes and forces around the drag head3 were all investigated on their cause and effect.
A model was set up, where each process and their interaction with the others were identified.
One main process in the drag head is the jetting production. A powerful jet of water is injected into the soil and this erodes part of the sediment under the drag head4.
Another main process is the cutting production5. What is not eroded away by the jets, is removed by the teeth at the back of the visor.
As the contribution of the processes to the forces and the production is known, the total performance can be calculated.
Along the way, this gave us very useful insight in the capabilities of the drag head and the trailing system, all the way to the requirements for the propulsion. Now, we will be able to continue to improve our drag heads even further. Any other students who would like to participate in that project are welcome to contact us5.
Gijs takes a new step in his career path. He is going to work for a well esteemed customer of us, so we will see him around in the dredging industry. Thanks Gijs, bon voyage!
Because of other activities these last weeks, my promised post about the DMC presentation had some delay. On October 10th, there was a symposium together with the Marine Institute Gdansk and the CEDA Environmental Commission and the CEDA Dredging Management Commission supported by Gdansk Science and Technology Park and the Baltic Ports Organisation1. The topic of the symposium was ‘Advances in Dredging Technology. My contribution was a presentation as DMC member2 on ‘Dredging technology developments versus requirements’.
Although dredging sounds like an old rusty trade, in fact, it is in constant movement and highly innovative when experienced from the inside. At the Dredging Management Commission, we have a separate focus group, that investigates the technological solutions that enable the stakeholders to efficiently manage a dredging project. A lot of ‘booby traps’ in the ‘Checklist For Successful Dredging Management’3 can be handled by applying the right technology. If there are issues with turbidity, e.g. one can apply a component as the ‘Plumigator®’4 attachment for the overflow in a trailing suction hopper dredge to comply with turbidity clauses in the contract. If the project has very narrow allowances for positioning, modern survey and control systems allow surgical precision dredging, to reduce overdredging and corresponding penalties.
All in all, we’ve identified more than 70 innovation over the last ten years, that have found a foothold in the dredging industry. These have been categorised to the field of technology: Components, Equipment, Industries, Initiatives, Methodology, Processes, Systems, Tools. Other descriptions that we’ve attributed to these innovations were their contribution in solving certain problems in dredging management, as they are found in the checklist. And how much effort they require and how much benefit they would yield. These last items are very subjective and still open for debate. More to follow later. But, at least the procedure can be laid out to recommend the best options for tackling certain problems in the ‘checklist.
We had a good discussion at the symposium about this topic and from the other focus groups (contract management, checklist, etc.). There were also cross-over opportunities with the CEDA Environmental Commission. At least, there are enough leads, that can be used for the next CEDA Dredging Days in Rotterdam.
As an illustration of the long way we’ve came in the dredging industry, the conference room in the control centre of the Port of Gdansk5, was decorated with interesting pictures from the construction of the port.